Metal and metal oxide granules and forming process

ABSTRACT

This invention relates to granules comprising a homogenous mixture of metal flakes and/or metal powder and metal oxide powder, and a binder. The process also relates to a process for producing such granules. The process includes the step of forming a mixture of metal flakes and metal oxide powder, forming the mixture into a homogenous blend, adding the blend, together with a binder, to a granulator to form granules, and drying the granules. Granules so formed containing aluminium, aluminium oxide and iron oxide find particular use as sensitisers and energisers in explosives compositions.

BACKGROUND OF THE INVENTION

[0001] THIS invention relates to a process for producing granulescontaining a homogenous mixture of metal flakes and/or metal powder andmetal oxide powder, and to granules containing a homogenous mixture ofmetal flakes and/or powder and metal oxide powder.

[0002] Metal and metal oxide flakes and powders and mixtures of metalpowders such as those described in South African patent no. 96/3387 areused as sensitisers and energisers in explosives compositions. A problemwith this type of metal powder is that when it is transported, thepowder is compacted in the bottom of the container in which it iscarried, making it difficult to unload the powder from the container.

[0003] This is particularly troublesome when metal powders are mixed viaan auger into an explosives composition from a feedbin, in situ, from amixing truck. Compacted powder in the bottom of the feedbin causescaking and hanging up, the metal oxides separate and an incorrect amountof powder, or composition of metal powder, is added to the composition.This leads to an inconsistent mixture throughout the volume of theexplosives composition, which means that the explosives composition isless effective.

[0004] U.S. Pat. No. 4,256,521 discloses a method of forming granulesfrom aluminium powder having a high proportion of fines of a size lessthan 80 microns, using a synthetic resin as a binder. However, thispatent does not disclose a method of forming a metal and metal oxidecomposition into a granule.

[0005] It is an object of this invention to provide a granule made froma metal and metal oxide composition, that is useful (in particular) as asensitiser and/or energiser in explosives compositions.

SUMMARY OF THE INVENTION

[0006] A first aspect of the invention relates to granules comprising ahomogenous mixture of metal flakes and/or powder metal and metal oxidepowder, and a binder.

[0007] The metal flakes are typically less than 0.35 mm, usually from0.05 to 0.35 mm, in size and the metal and metal oxide powder consistsof particles that are less than 10 microns in size.

[0008] Typically, the granules include more than 10%, by weight, metaloxide.

[0009] The granules may include up to 90%, by weight, metal oxide.

[0010] The metal flakes and/or metal powder and metal oxide powder maycomprise Al or Al alloy such as Al/Mg, and Al₂O₃ and other metal oxidessuch as Fe₂O₃, MnO₃ or MgO₂, preferably Fe₂O₃.

[0011] Advantageously, the Fe₂O₃ and Al are present in a ratio of atmost 3:1, by mass.

[0012] The metal flakes and/or metal powder and metal oxide powder arepreferably obtained from waste, typically aluminium dross and iron oxidefines.

[0013] Advantageously, the granules are in the form of porous prills.

[0014] Porous prills for use in explosives compositions typically have afree flowing apparent density of from 0.40 to 1.8 gm/cm³, preferablyabout 1.0 to 1.5 gm/cm³, most preferably about 0.9 gm/cm³ andadvantageously have a porosity of from 40% to 60%. The granules may varyin size from 300 to 6000 microns, typically from 30 to 900 microns.

[0015] The binder may be selected from polymers, polyalkylenecarbonates, resins etc. A typically binder is a starch-based aqueousbinder composition. Usually, the binder will not exceed 10%, by weight,of the composition. Another preferred binder is sodium silicate.

[0016] The granules may also include fluxing compositions such as metalsalts, resins such as guar gum, Shellac or ladotol and other stearins torender the granule water resistant and resistant to decay, andsensitisers such as expanded polystyrene, micro-balloons, and glass tomodify the density of the granules.

[0017] According to the second aspect of the invention there is providedan explosives composition comprising from 2% to 50%, by weight, of themetal and metal oxide porous prills described above, from 2% to 7% byweight of a fuel, typically an organic fuel, and from 50% to 95%, byweight, ammonium nitrate.

[0018] In the case of a dry ANFO explosive, the explosive compositiontypically includes 50% to 94% by weight of the composition ammoniumnitrate porous prills, 5% to 6% by weight of the composition fuel oiland 5% to 30% by weight of the composition metal and metal oxide porousprills described above.

[0019] In the case of heavy ANFO blends and doped emulsion blends, thecomposition typically comprises 30% to 90% emulsified ammonium nitrate,20% to 50% ammonium nitrate prills and 3% to 13% metal and metal oxideporous prills as described above.

[0020] A third aspect of the invention relates to a process forproducing granules containing a homogenous mixture of metal flakesand/or metal powder and metal oxide powder, the process including thesteps of:

[0021] 1. forming a homogenous blend of finely ground metal flakesand/or metal powder and metal oxide powder in a blender;

[0022] 2. adding the blend, together with a binder, a granulator to formgranules containing a homogenous blend of finely ground metal flakesand/or metal powder and metal oxide powder; and

[0023] 3. drying the granules.

[0024] Advantageously, an adherent, typically an organic fuel such asdiesel or oleic acid, is added to the homogenous blend, to form anadhered homogenous blend which is added to the granulator.

[0025] The metal flakes, metal powder and metal oxide powders mayinclude Al and Al₂O₃ and other metal oxides such as Fe₂O₃, MnO₃ or MgO₂,preferably Fe₂O₃.

[0026] The metal flakes, metal powder and metal oxide powder arepreferably obtained from waste, typically aluminium dross and iron oxidefines.

[0027] The aluminium dross is processed to form aluminium flakes andpowder and metal oxide powder. The aluminium content of the mixture isdetermined and sufficient iron oxide is added to the mixture to form aratio of Fe₂O₃ to Al of at most 3:1.

[0028] Admixtures such as micro-balloons, coal dust and magnesium may beadded to the mixture in step 1 to modify the sensitivity, reactivity andignition temperature of an explosive composition into which the granulesare added.

[0029] Advantageously, the dried granules are separated and classifiedaccording to size after step 3.

[0030] The dried granules may be coated with a water-resistant compound.

BRIEF DESCRIPTION OF THE DRAWING

[0031] The invention will now be described in more detail, by way ofexample only, with reference to the accompanying drawing which shows aschematic diagram of a process according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0032] Metal and metal oxide powders and flakes to be processed inaccordance with the invention include metal flakes and metal powders foruse in the explosives industry, and also for use in pyrometallurgy(hot-topping and de-oxidants), pyrotechnics, solid fuels, and in themanufacture of metal salts.

[0033] The granules of the invention are made from a homogenous mixtureof metal flakes and/or metal powder and metal oxide powder. The granulesinclude a binder which holds the powder and flakes together, with thepowder in close proximity to the flakes. The granules may also includeother constituents such as sensitizers, and may be coated with waterresistant compounds.

[0034] The metal flakes and/or metal powder comprise finely groundaluminium or an alloy of aluminium such as Al/Mg. The metal oxide isselected from Al₂O₃, Fe₂O₃, MnO₃ or MgO₂, or a mixture thereof. Typicalmixtures of metal and metal oxide powders and/or flakes are described inSouth African patent no. 96/3387, the disclosure of which isincorporated herein by reference.

[0035] It is of the utmost importance that the metal flakes are in ahomogenous mixture with the metal and metal oxide powder. The homogenousmixture ensures intimate contact between the metal and the metal oxide,which acts as fuel when the granules are used, for example as asensitiser in explosives compositions. If there were no homogenousmixture, the metal oxide would form unreactive pockets within thegranule, which negatively affects the combustion of the granule.

[0036] The Al flakes and Al₂O₃ powder is obtained from residues in theform of dross, skimmings, shavings and grindings from aluminium andaluminium production from primary and secondary operations which areoften destined for landfill. The Fe₂O₃ powder is obtained from ironoxide fines obtained, for example, from processes carried out on thetailings from the mining of ore bodies or other production processes.The other metal oxides (MnO₃ and MgO₂) may also be obtained from waste.

[0037] Referring to the drawing, in accordance with the invention,aluminium dross 10 is milled in an air swept ball mill 12 to produce Alflakes having a maximum width of 0.05 mm to 0.35 mm and a fine powderwith particles of the size of 10 microns and less. The powder is made upfrom Al, Al₂O₃ and small amounts of inert compounds such as silica andmetal salts. Air extraction in the air swept ball mill removes some ofthe very finely ground Al₂O₃ powder and the inert compounds. The amountof Al and Al₂O₃ in the powder and flakes so-formed varies from onesource of aluminium dross to another. A mixture of powder and flakesso-formed may comprise as little as 10% by weight Al and up to 98% byweight Al, the rest being made up mainly by Al₂O₃. Where the mixture ofpowder and flakes so-formed has a very low Al content, for example lessthan 25% by weight thereof, it is necessary to increase the Al contentby adding higher grade Al flakes thereto. The higher grade Al flakes maybe obtained from shavings, or grindings from aluminium production. Themetal and metal oxide powder and flakes so-formed having an Al contentof greater than 25%, by weight, and may be used as is, or mixed withanother metal oxide powder 14, typically Fe₂O₃ powder obtained from ironoxide fines, to provide a composition of metal and metal oxide powderand flakes which may be used in explosives compositions. Ideally, Fe₂O₃is added to ensure a stoichiometric ratio of Fe₂O₃ to Al of 3:1. A lowerratio of Fe₂O₃ to Al may be suitable in applications where additionalgas energy is required in an explosives composition.

[0038] Table 1 below shows the amount of Al and Al₂O₃ in milled Alobtained from Al dross, and Table 2 below shows compositions of metalflakes and metal oxide powder which are to be formed into the granulesof the invention. Composition 1 comprises Al and Al₂O₃. Compositions 2to 5 comprise Al, Al₂O₃ and Fe₂O₃. TABLE 1 Milled Dross 1 2 3 4 5 % Alin milled Al by weight 80 50 75 50 30 % Al₂O₃ in milled Al by weight 1540 20 40 65 % Inerts by weight 5 10 5 10 5

[0039] TABLE 2 Composition 1 2 3 4 % milled Al by weight 100 40 65 40 %Fe₂O₃ powder by weight (97% purity) 0 60 35 60 % Al₂O₃ in composition byweight 15 16 13 26 % Al metal in composition by weight 80 20 49 12 %metal oxide in composition by weight 15 76 48 86 % inert compounds byweight 5 4 3 2

[0040] The metal and metal oxide powder and flakes composition willgenerally be made up by 10% to 90%, by weight, Al and 10% to 90%, byweight, metal oxide.

[0041] The abovementioned compositions of metal flakes and powder andmetal oxide powder are prepared in bulk quantities (i.e. 1 to 10 tons ata time). To produce compositions 2 to 5 (ie the compositions thatcontain Al, Al₂O₃ and another metal oxide (Fe₂O₃)), bulk quantities ofthe milled Al and Al₂O₃ flakes and powder are mixed with bulk quantitiesof the Fe₂O₃ powder. In these circumstances, the amount of Al in themilled Al and Al₂O₃ flakes and powder derived from aluminium dross ismeasured and the amount of Fe₂O₃ powder added is altered according tothe percent Al in the milled Al and Al₂O₃ flakes and powder. Table 3below shows the percentage of milled Al and Al₂O₃ powder and flakesadded to the total tonnage of the final composition of milled Al andAl₂O₃ and Fe₂O₃, depending on the percentage Al therein. TABLE 3 1 2 3 45 % Al purity in milled Al and 60 50 40 30 25 Al₂O₃ flakes and powder %Al and Al₂O₃ flakes and 36 40 45 52 57 powder in Al and Al₂O₃ and Fe₂O₃composition % Al in Al and Al₂O₃ and 21 20 18 15 14 Fe₂O₃ composition

[0042] The abovementioned compositions are then formed into granules,typically porous prills, in a granulator using a suitable binder. It ismost important that the granules contain a homogenous mixture of flakesand powder, so that the metal is in intimate contact with the powder toensure that the metal reacts with the metal oxide, in use. If there isno homogeneity, clusters of powder would result, and this negativelyeffects the reaction of the metal with the metal oxide.

[0043] Before granulation, the composition of metal flakes and powderand metal oxide powder are then blended in a blender 16 (for example aribbon blender or paddle mixer typically running at 30-100 rpm), to forma homogenous mixture of metal flakes and powder and metal oxide powder.An adherent 18 (typically an organic fuel such as diesel or oleic acid),is added to the blender to adhere the metal flakes and powder and metaloxide powder together in an homogeneously blended mixture. Fluxingagents such as metal salts may be added to the blend forpyrometallurgical applications. Other sensitisers such as expandedpolystyrene, micro-balloons, glass etc. may be added to the blend toincrease the sensitivity of an explosives composition in which thegranules are used, and also to alter the density of the granules.

[0044] From the blender 16, the homogenous blend is sent to a granulator20. The granulator 20 includes a stainless steel drum which is liquidcooled, to ensure that the composition remains cool during thegranulation process (heat caused by friction in the granulator couldresult in an exothermic reaction). Housed in the drum is a series ofmixer blades located on a central driven shaft. The mixer blade designand angle, and the linear speed of the blades are selected to determinethe size and porosity of the granules (which are porous prills).

[0045] An operator begins the granulating process by continuouslyfeeding the adhered blended mixture into the granulator 20, whilespraying a binder 22 into the granulator 20 at the same time. Theoperator will control the size of the granules and porosity thereof byadjusting the rate at which the homogenous blend and binder is fed intothe granulator, and the speed of the blades. For small granules of ahigh porosity, the granulator is run at a high speed of 800-1000 rpm.The operator monitors the build-up of granules in the granulator and thepneumatic valve on the side of the granulator is opened periodically todischarge green granules from the granulator.

[0046] The design of the granulator 20 also permits the inclusion in theproduction process of admixtures such as density modifiers once thebinders have been introduced into the compositions being prilled.

[0047] Many binders may be used. Binder properties which are essentialin production are as follows:

[0048] 1. The binder must mix uniformly with the composition.

[0049] 2. Provide sufficient green strength to allow for furtherprocessing.

[0050] 3. The binder must not decompose during the processing of thegreen body.

[0051] 4. The binder in most application must burn out completely (inall atmospheres preferably leaving minimal ash residue).

[0052] Binders such as Dextrin, starch, polyalkylene carbonates, resinsand many others, can be used in the agglomeration and production ofporous prilled granules. The choice of binder used is determined by theend use of the prill. Aqueous dextrin has been found to be useful in theproduction of prills according to the invention for use in explosivescompositions, where very finely divided metals and metal/metal oxidepowders are prilled.

[0053] Sodium silicate may be used as a binder in explosives andpyrometallurgical applications and high alumina cements in order tomaintain prill integrity in rough handling conditions and amongst othercharacteristics, slow down or accelerate the ignition of thecompositions being introduced. Certain binders have the chemicalattributes required to modify reaction/ignition temperature withoutadmixtures such as many metal salts. They are also water and solventresistant and do not require that the prilled products need to beadditionally coated following production.

[0054] Following the granulating/prilling process in the granulator 18,the green granules are conveyed to a vibrating screen 24 (if desired),which assists in breaking any agglomerated green product, then to arotary drier 26, and lastly to a final infra-red drying stage 28.

[0055] The granules may be produced with, or coated with,water-resistant agents such as resins for example Shellac or ladotol torender the granule water-resistant for particular applications. However,in some applications, for example for use in emulsion explosives, thegranules are not made water resistant, so that the granules break downwhen added to the emulsion mixture.

[0056] Granules so produced may vary in size from 30 microns to 30 mm indiameter.

[0057] Preferred granules of the invention are porous prills.

[0058] The size of granules for explosives compositions could be from300 microns to 6 mm, with a free flowing apparent density (ASTMSTD) offrom 0.4 to 3.0 gm/cm³. The usual density for a bulk explosives mix isabout 0.92 gm/cm³ and the porosity of the granules may be from 40% to60%.

[0059] In a preferred embodiment, the metal and metal oxide granules areused as a sensitizer or energiser in dry ANFO mixes and heavy ANFOmixes, doped emulsion blends and packaged explosives preparations.Typically, the granules are added in an amount of from 2% to 30% byweight (usually not more than 10% by weight) of the explosivescomposition which further comprises from 2% to 5% by weight of fuel,typically an organic fuel such as diesel, and from 30% to 90% by weightof the composition ammonium nitrate. Explosive compositions normallycontain about 85% to 96% ammonium nitrate and the presence of thegranules of the invention can allow for a reduction of ammonium nitrateof up to 50%, of the composition.

[0060] Table 4 below provides examples of typical dry ANFO mixes andTable 5 below provides examples of typical heavy ANFO blends utilisingthe homogenous granules of metal flakes and powder and metal of theinvention. TABLE 4 1 2 3 4 5 6 Ammonium Nitrate (porous prills) 65 70 7580 85 90 % by mass of the composition Fuel Oil 5.5 5.5 5.5 5 5 3 % bymass of the composition Metal Powder Granules 29.5 24.5 19.5 15 9.5 7 %by mass of the composition Al Metal 20 20 20 20 20 20 % by mass of themetal powder granule Al₂O₃ 16 16 16 16 16 16 % by mass of the metalpowder granule Fe₂O₃ 60 60 60 60 60 60 % by mass of the metal powdergranule Free Flowing Apparent Density of Metal 1.4 1.4 1.4 1.4 1.4 1.4Powder Granules gm/cm³ Size of granule microns 300-890 300-890 300-890300-890 300-890 300-890

[0061] TABLE 5 1 2 3 4 5 6 7 8 Emulsified Ammonium Nitrate 55 60 60 6060 65 65 65 % by mass of the composition Ammonium Nitrate Porous Prill40 34 33 32 31 25 24 24 % by mass of the composition Metal PowderGranules 5 6 7 8 9 10 11 10 % by mass of the composition Al Metal 20 2020 20 20 20 20 80 % by mass of the metal powder granule Al2O3 16 16 1616 16 16 16 20 % by mass of the metal powder granule Fe2O3 60 60 60 6060 60 60 0 % by mass of the metal powder granule Free Flowing ApparentDensity 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.2 of Metal Granules gm/cm3 Size ofgranule microns 300-890 300-890 300-890 300-890 300-890 300-890 300-8901000-2000

[0062] The granulated metal powder granules made according to theinvention have many advantages including:

[0063] 1. The flow-handling of the granules is far better than that ofpowder and stops caking and hanging up of the product in feed bins andimproves calibration and delivery of the product, with less wear onpumps and augers;

[0064] 2. As the metal powder is bound in granules, there is much lessdust;

[0065] 3. There is no segregation of the aluminium, aluminium oxide andiron oxide in the granule, ie. the granule contains the metal componentsin the powder homogeneously;

[0066] 4. The compressive strength of the granules can be varied (byvarying the amount and type of binder), according to need;

[0067] 5. The granules can be classified into particular sizes forparticular applications;

[0068] 6. It is convenient to add desired compounds or compositions tothe powder, prior to granulation to alter the characteristics of thegranules. Furthermore, certain admixtures can be added prior togranulation to modify the oxygen balance which affects the energy yieldof the granule.

[0069] 7. When used in an explosives composition, the granules reducethe density of the composition and there is better distribution of thesensitizer/energiser within the explosives composition. Also, thedensity of the granules can be adjusted to adjust the density of theexplosives composition. Such compositions are also more stable and saferto store, handle and transport.

[0070] 8. A starch-based aqueous binder composition is relativelyinexpensive and the starch combusts and thus plays an active role in anexplosives reaction when the granules are used in explosivescompositions.

[0071] 9. The granules can be coated to make them resistant to waterwhen water dissolvable binding systems are used in explosivecompositions.

[0072] 10. If there are any free heavy metals in the powderedcomposition which may affect the base product stability, for example, PHonce prilled, the binder composition, which is stable and additionalcoating thereafter will prevent any potential emulsion breakdown, in thecase of explosives compositions.

EXAMPLE 1

[0073] Aluminium dross was obtained from the production of aluminiumalloys from secondary and primary metal. The aluminium dross was milledin an air swept ball mill to produce aluminium flakes having a maximumwidth of 0.5 mm to 0.1 mm and a fine powder which included Al, Al₂O₃ andsmall amounts of inert compounds such as silica. Air extraction in theair swept ball mill removed some of the very finely ground Al₂O₃ powderand inert compounds. The flakes and powder so-produced were tested andfound to contain 50% Al, the rest being made up mainly by Al₂O₃. 400 kgof this Al and Al₂O₃ powder and flakes was then mixed with 600 kg ofFe₂O₃ powder obtained from iron oxide fines to provide a composition ofmetal and metal oxide powder containing 20%, by mass, Al, 20%, by mass,Al₂O₃, and 60%, by mass, Fe₂O₃.

[0074] The metal powder composition was sent to a ribbon blender whichwas running at a speed of 30 rpm, to form it into a homogenous mixtureof metal flakes and powder and metal oxide powder. 3 kg of diesel wasadded to the blender to adhere the composition together, in a homogenousblend.

EXAMPLE 2

[0075] The adhered homogenous composition described in Example 1 wasthen mixed with a starch-based aqueous binder to provide metal powdergranules according to the invention.

[0076] The starch-based aqueous binder composition was formed from 40parts by weight of a starch, namely dextrin yellow, 60 parts by weightwater, 9 parts by weight of a thickener such as borax and 1 part byweight sodium hydroxide which is also a thickener. 0,4 kg of dextrinyellow, 0,09 kg of borax and 0,01 litre of sodium hydroxide solution wasadded to the solution to form the starch-based aqueous bindingcomposition.

[0077] 1000 kg of adhered homogenous composition described in Example 1was fed into a high-speed granulator. The blade design of the mixer wasdesigned to provide a maximum shearing effect in order to produce smalldiameter granules. The mixer was operated at a speed of 920 rpm (thehigh speed ensured a high porosity of the granules) and 100 kg of thestarch-based binder composition described above was added to thegranulation mixer from a sprayer, at 30 ml/m. Granules were formed in 5minutes.

[0078] From the granulator, the granules were fed into a tumbling millwhich reduced agglomerates and then into a rotary dryer which wasoperated at a temperature of 250° C. From the rotary dryer, the driedgranules were fed into a multi-deck vibrating screen which classifiedthe granules into different sizes.

[0079] From the vibrating screen, the classified granules wereintroduced into a flow mixer which coated the granules with a waterresistant agent (oleic acid).

[0080] The granules so produced had a free flowing apparant density of1.4, a porosity of 45%, and a diameter of from 30 to 6000 microns.

1. Granules comprising a homogenous mixture of metal flakes and/or metalpowder and metal oxide powder, and a binder.
 2. Granules according toclaim 1 wherein the metal flakes are less than 0.35 mm in size. 3.Granules according to claim 2 wherein the metal flakes are from 0.05 to0.35 mm in size.
 4. Granules according to claim 2 wherein the powderconsists of metal and metal oxide particles that are less than 10microns in size.
 5. Granules according to claim 1 including more than10%, by weight, metal oxide.
 6. Granules according to claim 5 includingup to 90%, by weight, metal oxide.
 7. Granules according to claim 2wherein the metal flakes and/or metal powder is Al or Al alloy and, themetal oxide Al₂O₃ and/or other metal oxides.
 8. Granules according toclaim 7 wherein the other metal oxides is/are Fe₂O₃, MnO₃ or MgO₂. 9.Granules according to claim 8 wherein the other metal oxide is Fe₂O₃.10. Granules according to claim 9 wherein the Fe₂O₃ and Al are presentin a ratio of, at most, 3:1, by mass.
 11. Granules according to claim 5wherein the metal flakes and/or metal powder and metal oxide powder areobtained from waste.
 12. Granules according to claim 1 in the form ofporous prills.
 13. Granules according to claim 12 for use in explosivescompositions which have a free flowing apparent density of from 0.40 to1.8 gm/cm³.
 14. Granules according to claim 13 for use in explosivescompositions which have a free flowing apparent density of 1.5 gm/cm³.15. Granules according to claim 14 for use in explosives compositionswhich have a free flowing apparent density of about 0.9 gm/cm³. 16.Granules according to claim 12 for use in explosives compositions whichhave a porosity of from 40% to 60%.
 17. Granules according to claim 12which have a size from 300 to 6000 microns.
 18. Granules according toclaim 18 which have a size from 30 to 900 microns.
 19. Granulesaccording to claim 1 wherein the binder is starch.
 20. Granulesaccording to claim 1 wherein the binder is sodium silicate.
 21. Anexplosives composition comprising from 2% to 50%, by weight, of theporous prills defined in claim 12, from 2% to 7% by weight of a fuel,and from 50% to 95%, by weight, ammonium nitrate.
 22. A dry ANFOexplosives composition comprising 50% to 94% by weight of thecomposition ammonium nitrate porous prills, 5% to 6% by weight of thecomposition fuel oil, and 5% to 30% by weight of the porous prillsdefined in claim
 12. 23. A heavy ANFO blend or doped emulsion blendcomposition comprising 30% to 90% emulsified ammonium nitrate, 20% to50% ammonium nitrate prills and 3% to 13% of the porous prills definedin claim
 12. 24. A process for producing granules containing ahomogenous mixture of metal flakes and/or metal powder and metal oxidepowder, the process including the steps of:
 1. forming a homogenousblend of finely ground metal flakes and/or metal powder and metal oxidepowder in a blender;
 2. adding the blend, together with a binder, agranulator to form granules containing a homogenous blend of finelyground metal flakes and/or metal powder and metal oxide powder; and 3.drying the granules.
 25. A process according to claim 24 wherein anadherent is added to the homogenous blend, to form an adhered homogenousblend which is added to the granulator.
 26. A process according to claim25 wherein the adherent is an organic fuel.
 27. A process according toclaim 26 wherein the organic fuel is diesel or oleic acid.
 28. A processaccording to claim 24 wherein metal flakes and metal powder are Al metaland the metal oxides are Al₂O₃ and another metal oxide or oxides.
 29. Aprocess according to claim 28 wherein the other metal oxides are Fe₂O₃,MnO₃ or MgO₂.
 30. A process according to claim 28 wherein the othermetal oxide is Fe₂O₃.
 31. A process according to claim 24 wherein themetal flakes and metal powder and metal oxide powder are obtained fromwaste.
 32. The process according claim 25 wherein the homogenous blendof finely ground metal flakes and powder and metal oxide powder isobtained from aluminium dross which is processed to form aluminiumflakes and aluminium powder and Al₂O₃ powder.
 33. A process according toclaim 32 wherein the aluminium content of the processed mixture isdetermined and sufficient iron oxide is added to the mixture to form adesired ratio of Fe₂O₃ to Al.
 34. A process according to claim 24wherein the dried granules from step 3 are separated and classifiedaccording to size.
 35. A process according to claim 24 wherein the driedgranules are coated with a water-resistant compound.